1100 has 38mm mikuni carbs the 1200 has 44mm carbs.
Most who build the 1100 motor turn it into a 1200 motor its quite easy.
Get rid of the 1100 carbs and manifold and get a set from a GP1200 not a GPR.
You will need to add pulse lines for the carbs as well.
Start a thread on building your ski and all the Raider guys will pitch in and tell you how to get that Raider over 65 mph
Your crank is good your cases are good (need pulse lines) you need 1200 carbs or 46mm mikunis get a set of 1200 cylinders and pistons and you have a 1200 motor.
You will want to swap out the electrical system as well and I think the 1100 Raider has the same pump already.
Might as well raise the compresion while your at it as well.